The word "合璧" is formed by combining the character "合", meaning to join or combine, with "璧", which refers to a flat, circular jade disc used in ancient China. It originates from the literal practice of fitting two such jade discs together to form a complete circle, representing a seamless and perfect union. In modern usage, this compound word metaphorically denotes the harmonious integration of two elements, such as in arts or ideas, without any gap or discrepancy.